Rates of women who are opting for preventive mastectomies, such as Angeline Jolie, have increased by an estimated 50 percent in recent years, experts say. But many doctors are puzzled because the operation doesn't carry a 100 percent guarantee, it's major surgery -- and women have other options, from a once-a-day pill to careful monitoring.

Previous research has found that lack of sleep is associated with weight gain, but it was unclear whether the sleep problems drove the weight increase or vice versa.

To get a better handle on this chicken-or-egg issue, Canadian researchers tracked how people’s sleep patterns affected their weight over a six-year period. In the study, which appears in Tuesday’s issue of the journal Sleep, those getting six hours or less of shuteye nightly were more likely to become overweight or obese compared to those getting a solid eight hours of nightly slumber. And surprisingly, those getting nine or more hours of sleep were also more likely to become overweight or obese.

The findings indicate “a good night’s sleep might be good for body weight,” said Jean-Philippe Chaput, lead author of the study and a preventive medicine specialist at Laval University in Quebec City, Canada.

Double whammyThe weight gain in the short sleepers makes sense, Chaput said, because lack of sleep causes a double whammy. It leaves us too tired to exercise while at the same triggering changes in the body, such as a decrease in levels of the hormone leptin, that make us feel hungrier, so we tend to eat more.

Why the long sleepers would gain weight is not entirely clear, however. One explanation is that long sleepers may actually be short sleepers. They may be spending more time in bed but not actually getting good quality sleep, Chaput said.

“This is a warning to the public that sleep is critical to good health,” said Dr. Michael Sateia, chief of the sleep medicine section at Dartmouth Medical School in Lebanon, N.H.

The findings suggest that lack of sleep may be contributing to the rising rates of obesity, said Dr. Mary Susan Esther, director of the sleep center at the Charlotte Eye, Ear, Nose and Throat Clinic in Charlotte, N.C., and president-elect of the American Academy of Sleep Medicine.

Esther has already noticed in her own patients that adequate sleep is important for shedding pounds. “I always tell my patients who want to lose weight, be sure you get enough sleep,” she said.

In the study, 276 men and women, ranging in age from 21 to 64, answered questions about how long they slept each night at the beginning of the research and then again six years later.

Participants who initially reported sleeping five to six hours nightly were about 35 percent more likely to gain 11 pounds and and nearly 30 percent more likely to pack on enough weight to be deemed obese over the years than those who reported getting seven to eight hours of shuteye each night. Participants getting nine to 10 hours of sleep were 25 percent more likely to gain 11 pounds and more than 20 percent more likely to become obese than the ideal sleepers.

The increased risk of weight gain and obesity in the short and long sleepers held true even after controlling for other factors, such as initial weight and exercise levels.

For those who have having trouble sleeping, both Sateia and Esther said the first step is to incorporate good bedtime practices, including following a regular time for going to bed and avoiding excessive use of alcohol and caffeine.

Time to unwind
Although a visit to the doctor or a sleep specialist might be required to rule out medical conditions that can cause sleeping problems, both Sateia and Esther said the most common problem is people’s difficulty to unplug from the Internet or television at night to give themselves time to wind down.

Video: How tired are you?
Often, something as simple as turning off the computer or TV an hour before to going to bed can be enough to fix the problem, Sateia said.

For Mick Hager, 47, stress from his job in his late 30s was the beginning of a downward spiral that led to problems sleeping and weight gain. Hager, who lives in Green Bay, Wis., credits improving his sleep quality with helping him drop 104 pounds that he has kept off for seven years.

Hager said the key to his success was starting an exercise program and keeping a consistent nightly routine that involves going to bed at the same time and not doing anything strenuous for several hours before turning in.

“It was an entirely life-changing event,” Hager said of his enhanced slumber. “My quality of life improved, I felt better, and I no longer felt stressed or anxious.” And that in turn allowed him to keep up his exercise regimen and maintain his weight. “I don’t think I would have had the energy to work out if my sleep hadn’t improved,” he said.